The present invention relates to a protective device for producing very small bores in tubular components, especially in fuel injection nozzles for internal combustion engines. The present invention also relates to a method of producing such bores, especially very small bores, that open out into a hollow space in tubular workpieces, especially in fuel injection nozzles for internal combustion engines.
In the past, microbores were produced by a cutting or electrical discharge type of machining. Such methods are time consuming, tool intensive and in addition relatively imprecise. Finally, with such methods it is only possible to produce having bores circular diameters in workpieces. Furthermore, after the bores are produced their walls are relatively rough.
It is therefore an object of the present invention to be able to economically and precisely produce very small bores.
The protective device of the present invention is characterized primarily in that it is embodied as a hollow body that is at least partially energy reducing for laser beams. The method of producing a bore pursuant to the present invention is characterized primarily in that the wall of the workpiece is perforated by a laser beam for producing the bore, and in that after the laser beam has perforated the wall the energy of the laser beam within the hollow space of the workpiece is reduced to such an extent that the laser beam does not damage the wall of the hollow space that is disposed across form the produced bore.
As a consequence of the inventive configuration of the protective device as well as of the inventive method, the energy of the laser beam that exits the wall of the workpiece after the production of the microbore is so significantly reduced that the laser beam does not lead to damage of the workpiece or of the protective device. Very precise microbores having very smooth walls can be produced with the laser beam. The service life of the protective device can advantageously be extended by supplying it with compressed air and/or subjecting the device to a vacuum in order to cool the protective device.
Further specific features of the present invention will be described in detail subsequently.